1. Field of the Invention
The present invention relates to a developing device for an electrophotographic processor such as a laser beam printer, copy machine, facsimile, or compound machine, and more particularly, to a developing device for an electrophotographic processor which prevents toner from hardening due to long-term stopping of a developing portion.
2. Description of the Prior Art
A conventional developing device for an electrophotographic processor includes: a photosensitive drum which is conductive when irradiated only; a charging roller which induces high voltage on the photosensitive drum; an exposure portion which imprints image data corresponding to character or picture signals from a computer and to a portion of the photosensitive drum; a developing roller which adheres charged toner powder onto the photosensitive drum; a high-voltage transfer roller which draws the toner powder onto the paper from the photosensitive drum; a toner fixing portion which fixes the toner on the paper at high temperature and voltage; a feeding portion which conveys the paper to a given position; and a driving portion by which all the above-mentioned components are organically driven with one another.
When the developing device experiences a long period between printing jobs, thus the toner is not agitated, or when the device is transported on a long, rough road reducing void volume of the toner. The toner powder tends to harden due to its strengthening coupling force. As a result, the agitator must impart an increased driving torque to stir the toner, sometimes exceeding the range of torque of the motor, resulting in the inability to drive and the failure of the agitator.
A need exists for a developing device which discourages the hardening of toner over long-term storage and/or arduous transportation.
U.S. Pat. No. 5,489,976 for a Toner Replenishing Device for a Developing Device of an Image Forming Apparatus issued to Ichikawa, describes a toner replenishing device including an engaging member used to transfer a driving force from an external drive to agitate toner stored in a cartridge. Referring to FIGS. 2 and 3, the cartridge 42 includes an agitator 421 with a rotary shaft 421a. An engaging portion 5 is mounted on the protruding end of shaft 421a, and is engageable with a drive mechanism. The device also includes a drive transmitting portion 6, including a drive shaft 60 connected to a drive source. In the event that the drive shaft experiences an excessive load, such as when toner stored in the toner cartridge has hardened, engaging member 52 moves against the action of the coil spring 51 due to the rotation of the connecting member 61, thus the engaging member 52 and connecting member 61 are disengaged from each other. Continued rotation of the shaft induces the ridge 52c to jump into the groove 61f due to the action of the coil spring 51, causing a vibration that loosens the toner.
U.S. Pat. No. 5,655,195 for a Toner Cartridge for Developing Device Included in an Image Forming Apparatus issued to Ichikawa et al., describes a device including an agitator that loosens hardened toner.
U.S. Pat. No. 5,655,180 issued to Yasuda et al. describes a Toner Cartridge with a Rotary Element Which Is Attachable to and Detachable from a Developing Apparatus, which, referring to FIGS. 2 and 3, includes a blade 12 mounted on a cone 11. The cone is adapted to be driven by a drive shaft 25. Referring to FIG. 18, another embodiment provides for driving the cone with a set of bevel gears. Referring to FIG. 24A, the device includes a driving element with a spiral-formed face. The device is intended to be driven continuously by the drive mechanism of the device in which the toner cartridge is mounted.
U.S. Pat. No. 5,652,944 for Serial Electrophotographic Apparatus with First and Second Supply Chamber with Stirring Arrangements issued to Masuda et al., provides a rotatable pedal including a gear which meshes with a plurality of other gears to permit a user to drive a toner stirring mechanism within a toner cartridge. U.S. Pat. No. 5,572,301 for Developing Device to Which Drive Transmission From a Cartridge Is Cut Off issued to Shiratori, describes a toner cartridge including a grip connected to a stirring mechanism which may be rotated by the user. Although not shown, a coupling for receiving a drive force from the developing device is provided on the opposite side of the toner cartridge engaged with the gear 5.